Autonomic Nervous System Flashcards
Nerutransmitters
transfer information from nerve terminals across the synaptic cleft
Classification of the NS by location
peripheral and central
Central- brain and spinal cord
peripheral- everything else
Classification of the Nervous system by Function
autonomic and somatic
Autonomic Nervous system
Typically involves actions that are not under conscious control
ex: visceral functions (cardiac output, blood flow to vital organs, heart rate, digestions)
Somatic Nervous System
involves conscious function
EX: movement, respiration, posture
Sections of the Autonomic Nervous System
Sypmathetic and parasympathetic
both originate from central NS
Sympathetic exits at thoracolumbar
Parasympathetic exits at the craniosacral
Types of Efferent Nerves in the Autonomic NS
Preganglionic and Postganglionic
Preganglionic Neurons
originate int he CNS and connect to ganglia in peripheral NS
Postganglionic Nerurons
terminate on effector organs (heart, lungs, liver, bladder)
Ganglia
act as a relay station to pass messages in to postganglionic nerves
Afferent Neurons
regulate autonomic NS by sensing actions and providing feedback to CNS
info from effector organs to CNS
NT’s of the Autonomic NS
Acetylcholine (ACh) and Norepinephrine (NE)
Acetylcholine (ACh)
- released from cholinergic nerve fibers
- incudes almost all efferent nerve fibers (parasympathetic and sympathetic)
- pre ganglionic in parasympathetic AND sympathetic, post ganglionic in parasympathetic
- somatic nerve fibers to skeletal muscles
Norepinephrine (NE)
released from adrenergic nerve fibers
-includes most postganglionic SYMPATHETIC nerve fibers
Facts about ACh
-made from acetyl-CoA with enzyme choline O-acetyltransferase
synthesis occurs in mitochondria
-when its made its transferred to nerve terminal by choline transporter and stored in “quanta” vessicles at ther surface of the synapse
Release of ACh
- action potential is generated in nerve terminal
- influx of Ca++ into nerve terminal which interacts with vessicle membrane (quanta) and causes it to fuse w/terminal membrane
- pore opens into synapse, and releases hundreds of quanta into synaptic cleft
Binding of ACh
-in synaptic cleft ACh binds to acetylcholine receptors (cholinoreceptors) and you will get action
Acetylcholinesterase (AChE)
present in the synaptic cleft, enzyme that breaks down ACh into choline and acetate within seconds and terminates ACh’s action.
This is way to stop action of ACh
Adrenergic Nerve Fibers
postganglionic nerurons of the sympathetic nervous system
release NE (norepinephrine)
used in stressful situations, fight for flight
Actions of Adrenergic Nerve Fibers
increase heart rate mobilize energy stores increase blood flow to skeletal muscle divert blood flow from skin and internal organs during fight or flight dilate pupils and bronchioles
Termination of Adrenergic Actions
1) NE is metabolized by enzyme MAO
2) diffusion away from receptor site
3) reuptake into pre-synapse terminal by NET
4) acts with a receptor and causes an action
Receptors
- made of proteins designed to bind to specific molecules
- apon binding receptors pass on message using signaling proteins
many drugs based on this receptor-ligand interaction (agonists and antagonists)
Cholinoceptors (cholinergic receptors)
named after alkeloids that bind them
Muscarinic-at the effector organ level
Nicotinic-only at ganglion level
Adrenergic receptors (adrenoceptors)
alpha 1, alpha 2
beta 1, beta 2
dopamine
Functions of Parasympathetic NS
tronotrophic (energy storing)
takes care of everything at rest (digestions, storing energy, conserving energy)
Function of Sympathetic System
ergotrophic
energy expenditure
active during fight or flight
stimulates heart, increases blood sugar, mediates vasoconstriction of blood vessels…breaks down glycogen from liver, vasoconstriction. uses energy parasympathetic ns stores
Parasympathetic effect in CV
decreases heart rate
Sympathetic effects on CV
alters peripheral vascular resistance to manage BP
heart rate
contraction and force to manage CO
venous tone
renin production to manage renal blood flow
Presynaptic Regulation
Presynaptic alpha 2 receptors
activated by binding NE released from same nerves
binding=reduced release of more NE
Beta receptors- facilitate release of more NE
Post Synaptic Regulation
1) up or down regulation
2) action of one receptor is affected by action of other receptor
